It must be ensured during the treatment of special wastes by incinerating the waste in a drum-type furnace and during the subsequent afterburning of toxic flue gases in the afterburning chamber that the flue gases, contaminated with dioxins and furans, cannot enter the atmosphere through leaks between the individual treatment steps.
Infiltrated air must likewise be prevented from entering the afterburning chamber, from interfering with the combustion process, and from leading, as a result, to an increased consumption of primary energy.
To prevent infiltrated air from entering the drum-type furnace and the afterburning chamber attached thereto, or to prevent combustion gases from being discharged due to explosion the charge or feed side and the inlet side of the afterburning chamber are sealed against the rotary drum.
A seal between a first component formed by the rotary tube of a rotary drum-type and a second, stationary component has been known from DE 36 44 330. The first component has a radially outwardly projecting ring, which is surrounded by a ring housing, which is sealed by a compensator against the second component, and the two side walls of which contain concentrically arranged annular grooves at the inner surfaces. A sealing ring made of an elastic, flexible sealing material, as well as a support ring are axially displaceably arranged in these grooves, and one side of the support ring is in contact with the sealing ring, and the other side of the support ring is supported on coil springs, which press the sealing ring against the groove. The ring housing has guide holes, into which extend bolts, which are rigid parts of the second component and are parallel to the axis of rotation.
A device for sealing drum-type furnaces against stationary housings by means of radial sliding surfaces on a stationary sliding ring and on a radially and axially movable, rotating wear ring has been known from DE 37 44 602. A support ring was modified such that, being the core of the seal, it assumes all functionally important tasks. This ring is axially movable due to a plurality of hinged straps, is pretensioned by a plurality of tension springs, and is additionally connected to the rotating drum via tangential connecting rods. An annular groove, provided in the support ring, is used to accommodate a two-part wear ring. The collar is looped around as a band and is forcibly deformed into a single-wave expansion compensation means. A spring element provided in the valley of the wave guarantees the dimensional stability of the expansion wave pulled in toward the axis of the drum. The space is kept free of solids in the area of the seal by a stripper and an opening in the stationary housing, and sealing is improved.
Bowden cable seals, which consist of a plurality of wearable sealing segments, which are guided radially movably by divided plate flanges and are pressed against the sealing surfaces of the jacket of the drum-type furnace by means of one or more circular and weight-loaded cables, are frequently used on drum-type furnaces for incinerating special wastes. Sealing is ensured by a sliding seal, which consists of an asbestos-free material containing a high percentage of graphite.
The disadvantage of the use of this bowden cable seal is the different pressing force on the sealing segments, which applies unequal sealing pressure on the sealing segments because of the subsiding normal forces when viewed in the circumference. This leads, as a result, to different degrees of wear.
To achieve a sufficient minimum pressing force on all segments, a higher pressing force must be applied to the first segments than the minimum pressing force necessary for the segments located farther away.
Another disadvantage of this seal is the leaks at the overlapped joint areas of the segments, so that flue gases can escape or infiltrated air can be drawn in the radial direction as well as in the axial direction here.
Additional leaks in the axial direction develop as a result of the chambering of the individual sealing segments having gaps, which are formed at the joint areas of the chamber flanges.